Suppression of foliar and soilborne pathogens

ABSTRACT

Disclosed herein is a method for increasing the production of crops, particularly wheat and soybean, using herbicide resistant cultivars. In one aspect of this method, the method increases crop yield by diminishing the impact of the root diseases caused by  Gaeumannomyces  and  Rhizoctonia  species by treating the crop with an herbicide, in particular glyphosate. In another aspect the method for treating crops reduces the effects foliar pathogens and diseases, particularly fungal pathogens, such as rusts, including soybean rust, stem rust, stripe rust and leaf rust.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/515,339 filed Oct. 28, 2003, and U.S. ProvisionalPatent Application No. 60/532,758 filed Dec. 24, 2003, both of which areincorporated herein by reference.

ACKNOWLEDGEMENT OF GOVERNMENT SUPPORT

The Federal government may have certain rights in this technologypursuant to USDA Biotechnology Risk Assessment Research Grant number2001-03734.

FIELD

This disclosure concerns methods for increasing the yield of crops thatsubject to disease pressure, particularly from seed borne, soil borne orfoliar pathogens, such as fungi.

BACKGROUND

Commercial farming is a critical part of the economy. However crops aresubject to near constant attack by insects, fungi, bacteria and otherpathogens. When such pathogens encounter susceptible crops, such attackscan result in lower yield quality and can even destroy entire crops.Thus, pathogens cause substantial economic harm to growers and in someareas of the world contribute to famine.

Traditionally, farmers have relied upon conventional tillage methods todisrupt the soil and thereby control weeds, pathogens and volunteercrops. However, the current trend, particularly in the Pacific Northwestregion, is to use no-till or direct seed crop production methods toreduce soil erosion and the accompanying environmental degradationassociated with conventionally tilled fields. No-till and direct seedingmethods aim to reduce environmental degradation but generally requirethe use of herbicides to control weeds and volunteer crops.

Typically growers apply herbicides prior to planting to control weedssince the crop itself may be susceptible to the herbicide. However thedevelopment of herbicide resistant wheat varieties raises thepossibility of increasing wheat yields by applying the herbicide to thestanding crop. Unfortunately, weeds dying in the standing crop have beendemonstrated to result in carryover of fungal pathogens, which typicallyare unaffected by herbicides, from the dying weeds to the standing wheatcrop. Indeed, U.S. Pat. No. 5,972,689 to Cook et al. (Cook) disclosesthat spraying with an herbicide such as glyphosate controls weeds, butfavors the development of Rhizoctonia root rot in wheat. Because wheatis particularly susceptible to fungal pathogens, this carryover or“green-bridge” is a serious problem.

This green-bridge effect often leads to yield reductions associated withincreased disease pressure which are the result of increased soilbornepathogens present on dying herbicide-sensitive volunteer and/or weeds.For example, R. solani significantly reduced grain yields ofglyphosate-sensitive barley when glyphosate was applied three daysbefore planting. However, no significant yield depression was detectedwhen glyphosate was applied in the fall or three weeks prior to planting(Smiley et al. Plant Dis. 1992, 76, 937-942). These results demonstratethat a fresh source of R. solani inoculum, from the dying volunteer andweeds treated with glyphosate three days prior to planting, acted as agreen-bridge for the fungus to infect barley planted shortly afterherbicide application.

Another fungal disease of concern, take-all, is caused by Gaeumannomycesgraminis var. tritici (Ggt), which has been a persistent pathogenplaguing wheat around the world for over a hundred years. Take-all (Ggt)disease is present in the roots, crown, and basal stem of infected wheatplants. Severe Ggt infection can decrease grain yields by as much as50%. Symptoms of infection include stunting, blackened lower stems, andwhite heads. Take-all will commonly put out “runner-hyphae” toneighboring plants, so that a single site of infection is sufficient tocause multiple infections. Persistence through a green-bridge effect canoccur similar to that reported for R. solani. Studies conducted in NewZealand have shown that treatment of cereals with glyphosate increasesthe levels of infection with Ggt due to the green-bridge effect of theherbicide on couch grass (Harvey et al. Aglink 1/3000/3/82, 1982,Ministries of Agriculture and Fisheries, Wellington, New Zealand). Themost successful current form of Ggt control is through crop rotation,which is not always satisfactory for wheat production.

Nineteen Pythium species have been reported to be pathogenic to wheatroots. Pythium inoculum will remain active within the upper soil layerfor years, utilizing residues as a source of nutrients. Pythium isconsidered to be a primary colonizer and infection levels can be reducedby removing straw and debris from the field. Unfortunately, this is notan option in a no-till system.

The interaction between glyphosate treated plants and infection byPythium spp. has been investigated with numerous crop species. SoilbornePythium spp. were found to be the first and predominant root colonizersof glyphosate treated plants (Levesque et al. Mycological Research 1993,20, 307-312). This is an important observation since Pythium damage isoften overlooked by growers, even though significant yield lossresulting from Pythium infection can occur.

Another group of important pathogens that affect wheat include foliarfungal pathogens, such rusts. Rust pathogens are parasitic fungi thatinfect wheat, barley, oats, beans, corn, sorghum, and other plants. Eachrust pathogen is generally specific to its host and the location on theplant where infection occurs. The stem rust pathogen (Puccinia graminisf. sp. tritici) is a fungus that principally infects the leaf sheath ofwheat plants. The leaf rust pathogen (Puccinia recondita f. sp. tritici)infects wheat plants through the stomates. The stripe rust pathogen(Puccinia striiformis) is similar to leaf rust, but differs in thatinfections appear systemic due to colonization patterns on wheat leaves.

Soybean rust is another serious rust pathogen that causes crop losses.It has not yet been detected in the continental United States, but thefact that it is principally spread by wind-borne spores indicates it mayeventually reach major soybean growing areas in the United States.Soybean rust is caused by two fungal species, Phakopsora pachyrhizi andPhakopsora meibomiae. It has been reported in various countriesincluding Australia, China, Korea, India, Japan, Nepal, Taiwan,Thailand, the Philippines, Mozambique, Nigeria, Rwanda, Uganda,Zimbabwe, South Africa, Brazil, Argentina, and Paraguay. P. meibomiaehas been reported to be a weak pathogen. However, Phakopsora pachyrhiziis much more aggressive and recent introductions of P. pachyrhizi haverapidly spread causing severe damage in Zimbabwe, South Africa,Paraguay, and Brazil. Yield losses have been reported from 10-80%. Otherimportant fungal pathogens that affect soybeans include root rot causedby various species of Phytophthora.

There are few methods for controlling fungal diseases in wheat andsoybeans, and none of these methods are widely accepted as beingcommercially viable. For example, some root rot diseases can becontrolled through of crop rotation, that is, by not growing wheat inthe same field more than every third or fourth year. However, like mostother enterprises, agriculture has forced farmers to specialize in orderto compete. The United States grows some 150 different crops, but fewerthan 15 of these crops (including wheat and barley) occupy more than 90%of U.S. cropland, with the vast majority of farms specialized in theproduction of a single crop year after year on the same land, or two orat most three crops grown in a rotation on any given farm. Many wheatfarms in areas well-suited to cereals tend to grow wheat every year orat least every other year in the same fields. Moreover, in certainregions, such as in the Pacific Northwest, leguminous crops commonlyused in rotations do not bring the same levels of financial returns asdo continuous wheat cropping systems (see, Cook and Veseth Wheat HealthManagement; American Phytopathological Society: St. Paul, Minn., 1991).Therefore, crop rotation is not a feasible economic solution to reducedisease pressure in a continuously cropped no-till production system.

Many diseases of wheat, barley, and other crops are controlled bybreeding varieties of the crops with resistance to the pathogens.However, this approach has not worked for certain fungal diseases ofwheat, particularly root diseases. No commercial wheat is available thathas resistance to take-all, Rhizoctonia root rot, or Pythium root rot.Moreover, rust pathogens mutate at a relatively high rate, and thereforenew rust-resistant cultivars of wheat are needed approximately everyseven years.

Another method that is currently used to combat fungal infections is thetopical application of fungicides. Fungicides, although effective, areprohibitively expensive for growers and typically must be applied as apreventative, even if it is not certain that the plants will beinfected. Moreover many of the fungicides previously used have beenwithdrawn by the EPA. Compounds that are currently used are more easilydegraded and therefore are less harmful to the environment, but fungican quickly develop resistance to these compounds. Thus, fungicideapplications are even less desirable than before.

SUMMARY OF THE DISCLOSURE

Disclosed herein is a method for conferring resistance to pathogens oncrops, including wheat and soybeans. In one embodiment, the methodincludes treating a standing crop with an herbicide. In one aspect, themethod includes treating a crop with an herbicide, which increases thecrop's resistance to fungal pathogens. In one aspect of this method, themethod increases crop yield by diminishing the impact of the rootdiseases caused by Gaeumannomyces and Rhizoctonia species. In anotheraspect, the method increases the crop's resistance to foliar pathogens,particularly fungal pathogens such as rusts caused by various species,including stem rust, stripe rust, leaf rust and soybean rust.

Typically, the disclosed methods result in increased crop yields. Anyincrease in crop yield is desirable, however typically the methodproduces from about 5% to about 25% greater yield, and more typicallyfrom about 5% to about 15% greater yield relative to an untreated crop.

The herbicide used in embodiments of the disclosed methods typicallyincludes at least one of a sulfamoylurea, sulfonylcarboxamide,sulfonamide, sulfonylurea or glyphosate. In one aspect a combination ofherbicides, such as two or more of the herbicides listed above or one ofthe listed herbicides and one or more herbicide not listed, can beapplied to the crop. Typically the herbicide or herbicides are selectedwith reference to the particular wheat cultivar to be treated, forexample, an herbicide to which the particular cultivar is resistant canbe selected.

In one embodiment, the resistance of crops to various pathogens isinduced by applying an effective amount of an agricultural gradeformulation of a glyphosate-based herbicide (such as ROUNDUP® brandherbicide produced by Monsanto, St. Louis, Mo.) to a glyphosateresistant crop after emergence. Typically, the effective amount ofactive ingredient applied is from about 0.5 kg/ha to about 3.0 kg/ha,and more typically from about 1.0 kg/ha to about 1.5 kg/ha. In oneembodiment wheat is treated with formulations containing glyphosate at adensity from about 0.5 kg/ha to about 1.5 kg/ha of glyphosate. Inanother embodiment a soybean crop is treated with from about greaterthan about 1.0 kg/ha, such as from about 1.5 to about 3.0 kg/ha ofglyphosate. In one aspect of the method, an amount of glyphosate lessthan that typically recommended for weed control is effective to conferor induce pathogen resistance to a crop.

In one embodiment a crop is treated with glyphosate at a growth stagenot currently recommended for glyphosate treatment. For example, in oneembodiment glyphosate is applied to wheat at or after the 3 leaf stage,such as between the 3 leaf stage and the flowering stage. In anotherembodiment glyphosate is applied to soybean at growth stage afteremergence and before the flowering stage. In one aspect, glyphosate isapplied after symptoms of pathogen infection appear.

In embodiments of the method, treatment of herbicide resistant crop withan herbicide reduces disease on the crop for an extended period of time,and particularly for longer than the herbicide is active as an herbicideafter the treatment. Typically, the disease reduction extends for atleast about seven days after the treatment; more typically extends forat least about 21 days, and in certain examples extends for the life ofthe crop.

In another embodiment of the method, a crop is treated with an herbicideprior to emergence, and treated with the same or a different herbicideafter emergence. In yet another embodiment of the method a crop istreated with two or more separate applications of one or more herbicide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bar graph recording the number of sporulating lesionspresent 14 days following inoculation of two different soybean cultivarswith soybean rust spores and subject to five different conditions,demonstrating the suppression of soybean rust accompanying glyphosatetreatment of soybeans before and after inoculation with rust (treatmentsfollowed by the same letters are not significantly different at P=0.05,LSD test).

FIG. 2 is a bar graph recording the number of sporulating lesionspresent 21 days following inoculation of two different soybean cultivarswith soybean rust spores and subject to five different conditions,demonstrating the suppression of soybean rust accompanying glyphosatetreatment of soybeans before and after inoculation with rust (treatmentsfollowed by the same letters are not significantly different at P=0.05,LSD test).

FIG. 3 is a bar graph recording observed rust rating followinginoculation of the soybeans with rust and subject to five differenttreatment conditions (treatments followed by the same letter are notsignificantly different at P=0.05, Kruskal-Wallis One-Way Nonparametrictest).

DETAILED DESCRIPTION I. Introduction

The present disclosure illustrates the surprising result that thetreatment of herbicide resistant wheat, particularly glyphosateresistant wheat, with an herbicide, such as glyphosate, reduces diseasecaused by pathogens in the wheat. Moreover, the wheat exhibitspersistently superior pathogen resistance over an extended period oftime, after the herbicide is no longer effective as an herbicide. In oneembodiment, the deterrence of the pathogen is due to the accumulation ofglyphosate in the tissues the plant. In one embodiment the herbicideacts indirectly by inducing systemic disease resistance.

II. Herbicides and Herbicide Resistant Crops

Disease reduction on herbicide resistant crops can be accomplishedaccording to the methods disclosed herein. Suitable herbicides andherbicide resistant crops are known and will be readily apparent tothose of ordinary skill in the art. Moreover, methods for producingtransgenic herbicide resistant crops, including, without limitation,wheat and soybeans, are disclosed by U.S. Pat. Nos. 6,635,806,6,803,501, 6,750,383, which are incorporated herein by reference.

One herbicide for which resistant crops, including resistant wheat andsoybean cultivars, have been developed is N-phosphonomethylglycine,commonly referred to as glyphosate. Glyphosate is the active ingredientin glyphosate herbicides, such as ROUNDUP® brand herbicide produced byMonsanto (St. Louis, Mo.). Typically, glyphosate is formulated as awater-soluble salt such as an ammonium, alkylamine, alkali metal ortrimethylsulfonium salt. One of the most common formulations is theisopropylamine salt of glyphosate, which is the form employed inROUNDUP® brand herbicide.

Glyphosate is conventionally applied as an aqueous solution to thefoliage of plants to be killed, where it is taken up into the leaves andtransported throughout the plant. Commercial formulations of glyphosatemay also include one or more surfactants to facilitate penetration ofthe active ingredient into the plant leaves, as well as compounds toenhance rainfastness. Numerous U.S. patents disclose variousformulations of glyphosate and methods for their use, including U.S.Pat. Nos. 4,405,531; 5,118,338; 5,196,044; 5,639,711; 5,652,197;5,679,621; 5,750,468; 6,207,617; and 6,455,473. Each of these patents isincorporated herein by reference.

Glyphosate inhibits the shikimic acid pathway, which is responsible forthe biosynthesis of aromatic compounds including amino acids, such astryptophan, phenylalanine and tyrosine, as well as several secondarymetabolites. Specifically, glyphosate inhibits the conversion ofphosphoenolpyruvic acid (PEP) and 3-phosphoshikimic acid to5-enolpyruvyl-3-phosphoshikimic acid by inhibiting the enzyme5-enolpyruvylshildmate-3-phosphate synthase (hereinafter referred to asEPSP synthase or EPSPS). For purposes of the present disclosure, theterm “glyphosate” is intended to include any herbicidally effective formof N-phosphonomethylglycine (including any salt thereof) and other formswhich result in the production of the glyphosate anion in plants.

Glyphosate resistant crops, including glyphosate resistant wheat andsoybeans, are well known to those of ordinary skill in the art. Examplesof glyphosate resistant wheat are disclosed in U.S. Pat. Nos. 5,463,175;5,463,175; and 6,153,812. Production of lines of other plant species,including soybean, expressing a glyphosate-tolerance gene may beproduced by techniques known in the art. See, e.g. U.S. Pat. Nos.5,312,910; 5,310,667; 5,463,175. Each of these patents is incorporatedherein by reference.

III. METHODS AND EXAMPLES

Because herbicide treatment, including glyphosate treatment, typicallyimpairs certain plant defense mechanisms, dying herbicide sensitiveplants can function as a green-bridge, transferring pathogens to astanding crop. For example, glyphosate blocks the production of phenoliccompounds, such as lignin precursors and phytoalexins that arecomponents of the defense mechanisms and confer disease resistance.Because glyphosate causes the breakdown of plant defenses, glyphosaterenders glyphosate sensitive plants susceptible to pathogen invasion.This supplemental effect of glyphosate treatment has been termedGlyphosate Synergistic Interaction (GSI). GSI also provides a source orinoculum of pathogens that can attack the glyphosate resistant crop,thereby worsening the green-bridge effect.

As demonstrated herein, it has been surprisingly found that herbicidescan function indirectly to reduce pathogen damage to wheat. This resultis particularly surprising because herbicides have previously been shownto exacerbate the problems caused by fungal pathogens. Moreover, theherbicides have little or no direct anti-fungal activity and indeed thepathogen resistance is shown to be effective well after the herbicideitself dissipates from the treatment site. Accordingly, disclosed hereinare methods for increasing disease resistance in wheat, examples ofwhich include providing an herbicide resistant wheat crop and treatingthe crop with an herbicide, thereby conferring disease resistance on thecrop for an extended period of time.

One of the herbicides effective in the present methods, glyphosate, iscurrently applied to glyphosate sensitive wheat fields (prior toemergence of the crop) by producers in the fall or spring as aninexpensive yet effective way of controlling weed competition.Glyphosate has a wide spectrum of activity and controls 97% of theworld's worst weed problems. However, glyphosate has not been shown tobe effective against fungal pathogens, (see, Franz, J. E. DiscoveryDevelopment and Chemistry of Glyphosate. In, The Herbicide Glyphosate,Butterworths, London, 1985, pp 3-17). Moreover, some previous studieshave suggested that glyphosate encourages the growth of toxic fungi.

Disclosed embodiments of the present methods using glyphosate resistantwheat and soybean crops provide this same level of weed control duringthe early crop growth stages, and moreover reduce the effect ofpathogenic organisms and particularly fungal pathogens on wheat andsoybean crops. Moreover, embodiments of the present methods areeffective for treating crops that are already infected with a pathogen,having a curative effect on such crops. Therefore, in addition toeliminating weed competition, the present methods reduce losses to plantdiseases, thereby decreasing herbicide costs, increasing grain yields,and enhancing profitability.

For example, under severe stripe rust conditions, two Bobwhite cultivarsthat had not been treated with RoundUp were heavily infested with striperust, whereas glyphosate treated glyphosate resistant Bobwhite exhibitedonly moderate stripe rust symptoms. Bobwhite cultivars sprayed withBuctril/Harmony Extra (Buctril is commercially available from BayerCropScience, and Harmony Extra is commercially available from DuPont) orthe untreated control displayed severe stripe rust susceptibilitysymptoms and matured 2-3 weeks earlier than NILs treated with RoundUp.Buctril/Harmony Extra treated glyphosate resistant Bobwhite producedsignificantly (P=0.01) less grain than the glyphosate resistant Bobwhitetreated with glyphosate, regardless of root disease treatment. Visualdifferences in stripe rust severity typically were not apparent until 21days after herbicide application, which notably is well beyond the timeafter application that the herbicide exerts its direct herbicidaleffects.

The present results in both wheat and soybean are surprising for severalreasons, including that glyphosate was not previously found to beeffective for suppressing disease in glyphosate resistant crops. Theresults presented herein also are surprising because glyphosate isdirectly effective as an herbicide for only a short time and is notpersistent in herbicidally effective amounts. These results demonstratethat glyphosate application suppresses pathogen growth for an extendedperiod of time. The method is particularly effective in hindering thecolonization of leaf tissue by foliar pathogens. Moreover, the pathogensuppression extends to root pathogens, such as Rhizoctonia and Ggt.

In one embodiment, the methods disclosed herein can be used to treat acrop, such as wheat or soy crops, that are infected with a pathogen,such as a fungal pathogen, including seed borne, soil borne or foliarfungal diseases. For example, the treatment of infected crops withglyphosate is demonstrated herein to decrease fungal colonization ofcrops and to increase crop yield. This result is surprising because thefungal pathogens, such as stripe rust, soybean rust and the like,previously have not been thought to be susceptible to glyphosate. In oneembodiment the treatment of the crops includes two or more separateapplications of glyphosate. Thus, according to the embodiments disclosedherein crop yields can be increased by treating a crop before symptomsof infection are evident, following the appearance of infection, orboth. In exemplary embodiments, treatment of wheat and soybean bothbefore and after the emergence of foliar fungal infection resulted inincreased crop yield; In one embodiment, the crops are treated with fromabout 0.5 kg/ha to about 3.0 kg/ha of glyphosate in one or moreapplications. In one embodiment, from about 0.5 kg/ha to about 1.5kg/ha, such as from about 1.0 kg/ha to about 1.5 kg/ha of glyphosate isapplied. In one embodiment a first application of glyphosate of fromabout 0.5 kg/ha to about 2.0 kg/ha is made, followed by at least asecond application of from about 0.5 kg/ha to about 2.0 kg/ha. In oneaspect of this embodiment the crop is wheat and at least one applicationis made between the 3 leaf stage and the flowering stage. In anotheraspect of the method the crop is soybean and at least one application ismade between emergence and the flowering stage.

As demonstrated in the examples below, the reduced diseasesusceptibility of wheat treated according to the method also wasresponsible for increased grain yields observed for glyphosate treatedglyphosate resistant cultivars across trial growing locations,regardless of disease treatment.

The foregoing disclosure is further explained by the followingnon-limiting examples.

Example 1

This example describes the response of glyphosate resistant andglyphosate sensitive spring wheat to inoculation with soil pathogens asjudged by wheat yield. Inoculation simulates the green-bridge effect ofdying weeds and volunteer in a standing wheat crop. The soil pathogensassessed were: Rhizoctonia solani isolate AG-8 and Gaeumannomycesgraminis var. tritici. These pathogenic strains are prevalent in thePacific Northwest and were isolated from the region. They have beenmaintained by the Department of Plant Pathology and USDA researchers atWashington State University.

Near isogenic lines (glyphosate resistant and glyphosate sensitive) ofWestbred 926 and Bobwhite were seeded using a no-till drill at threedifferent sites (Lind, Davenport and Pullman, Wash.).

To introduce the root pathogens into the wheat seed for distributioninto the field, oat seeds, autoclaved and sterilized, were inoculatedfor each soilborne pathogen using isolated pathogen cultures. Oat seedsthat were non-inoculated, but sterilized and autoclaved, served as acontrol. Following two weeks of pathogen growth, the inoculated oatseeds were dried down for 2 days and screened for potentialcontamination. To establish a green-bridge, a mixture of 15% barley and20% oat inoculum seeds (by weight) were planted using a small plotno-till drill. One week after planting the introduced green-bridge, thewheat isolines were planted in rows adjacent to the barley green-bridgerows in a randomized, split-plot design, replicated in five randomizedblocks. Inoculum treatment served as the main plot, and response toherbicides as the subplot factor.

The results for Ggt and Rhizoctonia inoculation compared tonon-inoculated controls are illustrated in Table 1. In summary, withreference to Table 1, inoculation of wheat as described above can resultin depressed yields, as demonstrated in Lind in 2002. Yield losses areoften more severe in areas of lower rainfall such as Lind. TABLE 1 Wheatyield depression due to fungal inoculation, without herbicidetreatments, 2002. Yield Inoculation Herbicide Location (bu/acre) NoneNone Lind 13.5 Ggt None Lind 12.0 Rhizoctonia None Lind 12.9 None NoneDavenport 21.5 Ggt None Davenport 24.6 Rhizoctonia None Davenport 23.3None None Pullman 46.5 Ggt None Pullman 47.0 Rhizoctonia None Pullman47.5

Example 2

This example describes the effect of herbicide treatment on springwheat, averaged over all disease treatments, planted as described inExample 1. The appropriate herbicide was applied to each trial once theplants reached the 4-5 leaf stage with a custom built hand-pulledsprayer outfitted with a boom with a length of 16 feet with sprayshields on the side to minimize drift. In this manner, an entire plotwas treated at once with the appropriate herbicide rate. Entries thatwere resistant to glyphosate were treated with ROUNDUP® brand herbicide(0.63 kg/ha), available from Monsanto, St. Louis, Mo. Herbicidesensitive and resistant entries were treated with a common broadleafherbicide treatment (Buctril/Harmony) or a no-spray control. Introducedgreen-bridge barley and any other weeds were manually removed 7-10 daysafter spray treatment to simulate the time required for ROUNDUP to takeeffect and maintained weed-free conditions to provide an accuratecomparison to commercial weed management strategies needed to assesspotential herbicide/disease interactions.

The results of the herbicide treatment are recorded in Table 2. Withreference to Table 2, treatment of glyphosate resistant wheat withglyphosate resulted in higher yields in each trial. TABLE 2 Effect ofherbicide treatment on glyphosate resistant wheat averaged over allfungal inoculation treatments, demonstrating increased yield associatedwith glyphosate treatment. Herbicide Yield Resistance Herbicide Location(bu/acre) None None Lind 12.8 None Buctril/Harmony Lind 12.7 glyphosateres. Glyphosate Lind 14.2 None None Davenport 23.2 None Buctril/HarmonyDavenport 24.2 glyphosate res. Glyphosate Davenport 28.9 None NonePullman 47.0 None Buctril/Harmony Pullman 45.6 glyphosate res.Glyphosate Pullman 56.5

Example 3

This example describes the assessment of the disease response ofnon-inoculated glyphosate resistant spring wheat as described in Example1 and treated with glyphosate in comparison to inoculated near isogeniclines of glyphosate sensitive spring wheat. The results, recorded inTable 3, demonstrate increased yield accompanying glyphosate treatmentof non-inoculated wheat. TABLE 3 Yields of non-inoculated wheatdemonstrating increased yield of glyphosate resistant wheat due toglyphosate treatment, 2002. Herbicide Yield Inoculation ResistanceHerbicide Location (bu/acre) none None None Lind 13.5 none NoneBuctril/Harmony Lind 12.8 none glyphosate res. glyphosate Lind 14.2 noneNone None Davenport 24.6 none None Buctril/Harmony Davenport 23.6 noneglyphosate res. glyphosate Davenport 29.1 none None None Pullman 47.0none None Buctril/Harmony Pullman 45.0 none glyphosate res. glyphosatePullman 55.6Thus treatment of glyphosate-resistant wheat lines with glyphosateincreases yield, even in the absence of additional pathogen inoculum.

Example 4

This example describes the assessment of the disease response ofglyphosate resistant spring wheat inoculated with Ggt as described inExample 1 and treated with glyphosate in comparison to inoculated nearisogenic lines of glyphosate sensitive spring wheat.

The effect of herbicide treatment on the yield of glyphosate resistantwheat inoculated with Ggt is illustrated in Table 4. The yield forglyphosate treated, glyphosate resistant, Ggt inoculated wheat wassignificantly superior (P≦0.05) as compared to both untreated andBuctril/Harmony treated glyphosate sensitive wheat at each location.TABLE 4 Yields of Ggt inoculated wheat demonstrating increased yield ofglyphosate resistant wheat due to glyphosate treatment. Herbicide YieldInoculation Resistance Herbicide Location (bu/acre) Ggt None None Lind12.0 Ggt None Buctril/Harmony Lind 13.6 Ggt glyphosate res. glyphosateLind 14.4 Ggt None None Davenport 21.5 Ggt None Buctril/HarmonyDavenport 24.2 Ggt glyphosate res. glyphosate Davenport 28.7 Ggt NoneNone Pullman 46.5 Ggt None Buctril/Harmony Pullman 41.0 Ggt glyphosateres. glyphosate Pullman 57.0

Example 5

This example describes the assessment of the disease response ofglyphosate resistant spring wheat inoculated with Rhizoctonia solani asdescribed in Example 1 and treated with glyphosate in comparison toinoculated near isogenic lines of glyphosate sensitive spring wheat.

With reference to Table 5, glyphosate treatment of glyphosate resistantwheat resulted in enhanced yield at each location relative to untreatedand conventionally (13uctril/Harmony) treated glyphosate sensitivewheat. TABLE 5 Yields of Rhizoctonia inoculated wheat demonstratingincreased yield of glyphosate resistant wheat due to glyphosatetreatment. Herbicide Yield Inoculation Resistance Herbicide Location(bu/acre) Rhizoctonia None None Lind 12.9 Rhizoctonia NoneBuctril/Harmony Lind 11.7 Rhizoctonia glyphosate res. glyphosate Lind14.0 Rhizoctonia None None Davenport 23.3 Rhizoctonia NoneBuctril/Harmony Davenport 24.7 Rhizoctonia glyphosate res. glyphosateDavenport 29.0 Rhizoctonia None None Pullman 47.5 Rhizoctonia NoneBuctril/Harmony Pullman 50.6 Rhizoctonia glyphosate res. glyphosatePullman 53.9

Rhizoctonia and Ggt naturally prevail in areas receiving low and highlevels of precipitation, respectively. In trials planted in the low andhigh rainfall zones, grain yields of NILs treated with Buctril/HarmonyExtra were significantly (P=0.05) lower than NILs treated with RoundUpor the no-spray control.

Regardless of disease treatment or location, glyphosate treated RoundUpReady® (glyphosate resistant) spring wheat, produced significantly(P=0.001) more grain than glyphosate sensitive NILs treated withBuctril/Harmony Extra or the no spray control.

This demonstrates green-bridge transmission of fungal pathogens, such asRhizoctonia and Ggt, due to glyphosate application does not suppressyields of glyphosate resistant varieties; rather, glyphosate applicationincreases yields demonstrating that the glyphosate treated plants notonly resist the inoculated pathogens, but also other endemic pathogens,such as Puccinia spp. (rusts).

Example 6

This example describes the effect of herbicides on natural stripe rustinfection of NILs of Bobwhite with and without glyphosate tolerance. Thewheat was seeded and inoculated with Rhizoctonia and Ggt as described inExample 1. The yield results from the Pullman site are recorded in Table6.

With reference to Table 6, the glyphosate treated glyphosate resistantwheat Bobwhite NILs produced superior yields regardless of what pathogenhad been introduced. These results highlight the advantages of thedisclosed method for conferring disease resistance on herbicideresistant wheat. TABLE 6 Glyphosate induced yield enhancement ofBobwhite NILs in the presence of stripe rust in Pullman in 2002. YieldInoculation Cultivar Herbicide (bu/acre) None Bobwhite None 37.2 NoneBobwhite None 36.8 (res.) Rhizoctonia Bobwhite None 38.7 RhizoctoniaBobwhite (res.) None 33.9 Ggt Bobwhite None 37.7 Ggt Bobwhite None 32.8(res.) None Bobwhite Buctril/Harmony 33.0 None Bobwhite Buctril/Harmony31.8 (res.) Rhizoctonia Bobwhite Buctril/Harmony 39.4 RhizoctoniaBobwhite (res.) Buctril/Harmony 36.3 Ggt Bobwhite Buctril/Harmony 37.7Ggt Bobwhite Buctril/Harmony 26.4 (res.) None Bobwhite Glyphosate 44.9(res.) Rhizoctonia Bobwhite Glyphosate 40.0 (res.) GGT Bobwhite (res.)Glyphosate 49.0

Example 7

This example describes the effect of glyphosate treatment of glyphosateresistant wheat in varying amounts and at different times. Eightdifferent treatment regimens were applied to the hard white spring wheatvariety Macon, which is susceptible to stripe rust. Macon plots wereplanted at the Palouse Conservation Farm near Pullman, Wash. andsubjected to one of the following eight treatment regimens:

Treatment 1: no herbicide treatment and manual weed control;

Treatment 2: a 16 oz./A (0.50 kg/ha of active ingredient) application ofglyphosate, one-half the recommended rate of 32 oz./A (1.0 kg/ha ofactive ingredient), was made ‘on-label’ to glyphosate resistant wheat atthe 4-5 leaf stage.

Treatment 3: a first application of glyphosate at one-half (0.50 kg/haof active ingredient) the recommended density of 1.0 kg/ha was made toglyphosate resistant wheat at the 4-5 leaf stage according to themanufacturer's instructions. A second application of 16 oz./A (0.50kg/ha of active ingredient) glyphosate was made once moderate striperust symptoms appeared (42 days following the first glyphosateapplication).

Treatment 4: a 16 oz./A (0.50 kg/ha of active ingredient) application ofglyphosate, one-half the recommended rate, was made to glyphosateresistant wheat once moderate stripe rust symptoms appeared.

Treatment 5: a 32 oz./A (1.0 kg/ha of active ingredient) application ofglyphosate, the recommended full rate, was made ‘on-label’ to glyphosateresistant wheat at the 4-5 leaf stage.

Treatment 6: a first application of 32 oz./A. (1.0 kg/ha of activeingredient) glyphosate, the recommended full rate, was made ‘on-label’to glyphosate resistant wheat at the 4-5 leaf stage and a secondapplication of 32 oz./A. (1.0 kg/ha) glyphosate was made once moderatestripe rust symptoms appeared.

Treatment 7: a 32 oz./A. (1.0 kg/ha of active ingredient) application ofglyphosate was made to glyphosate resistant wheat once moderate striperust symptoms appeared. Treatment 8: a 48 oz./A. (1.0 kg/ha of activeingredient) application of glyphosate, 1.5 times the recommended rate,was made to glyphosate resistant plants at the 4-5 leaf stage.

The results of the treatments listed above are recorded in Table 7.TABLE 7 Yield of glyphosate-resistant wheat with variable timing ofadministration and amount of glyphosate. Stripe Stripe Rust Rust (96Stripe Rust (106 days days after (102 days after after Yield Treatmentplanting) planting) planting) (bu/A) No Spray  9, 40% 7-8, 70%  8, 50%55.4 No Spray  9, 30%  9, 50%  8, 50% 59.6 16 oz (52 days) 7-8, 10% 7-8,30%  8, 30% 60.2 16 oz (52 days) and 4-5, 10% 0-1, 10%  2, 10% 68.7 16oz (94 days) 16 oz (94 days) 7-8, 20% 2-3, 20% 2-3, 15% 52.7 32 oz (52days) 7-8, 20% 7-8, 40%  8, 60% 80.3 32 oz (52 days) and  9, 5% 1-2, 5% 3, 10% 74.5 32 oz (94 days) 32 oz (94 days) 7-8, 25% 0-1, 20%  2, 5%64.5 48 oz (52 days) 7-8, 2% 4-5, 10%  8, 20% 67.8

With reference to Table 7, stripe rust severity is characterized withtwo numerical indications. The first is a number characterizing thestripe rust severity on a scale of 0-9, with 0 corresponding to noinfection and 9 being a high level of spore activity and infection. Thesecond number is a percentage of the plants in the plot infected withthe rating described by the first number.

With continued reference to Table 7, glyphosate resistant Maconexperienced high levels of stripe rust infection when left untreated byglyphosate (rows 1 and 2). When glyphosate was applied to glyphosateresistant wheat at the 4-5 leaf stage, the 48 oz./A rate of glyphosatedid the best job of controlling stripe rust compared to the 16 oz./A and32 oz./A application. The higher rate of glyphosate clearly providedimproved control of stripe rust infection.

When glyphosate was applied to glyphosate resistant Macon once plantshad become moderately infected with stripe rust a curative effect wasobserved (rows 5 and 8). These “off-label” applications made 94 daysafter planting resulted in the formation of necrotic stripes on theleaves of the plants on the second day following glyphosate application.These necrotic stripes had been actively sporulating stripe rust at thetime of glyphosate application. The amount of time needed to controlstripe rust infection was found to be similar to when fungicides areapplied to wheat plants infected with stripe rust.

The best control of stripe rust was seen for treatments 3 and treatments6 (rows 4 and 7), which were treated with “split-treatments” ofglyphosate. The stripe rust activity for both of these treatments 94days after planting was similar to treatment 2 and treatment 4, beforethe second application of glyphosate was made. Once the secondglyphosate application was made, a curative effect against active striperust was observed. These treatments had the lowest levels of stripe rustinfection in the trial due to the initial fungicidal activity ofglyphosate from the first (4-5 leaf stage; 52 days after planting)applications and the curative effects of glyphosate from the secondapplications. A curative effect was also noted when glyphosate wasapplied only once for treatments 4 and 7. These results demonstrate thatthe methods disclosed herein for treating glyphosate resistant wheatprovide control of glyphosate sensitive weeds and control against thenegative effects associated with fungal pathogens.

Example 8

This example describes the suppression of soybean rust using glyphosatetreatment of glyphosate resistant soybean varieties.

Two different Roundup Ready soybean lines were used: Line 1 (purpleflowers/grey pubescence) and Line 2 (white flowers/grey pubescence).Both lines are glyphosate resistant and have been classified as maturitygroup 3, with white or purple flowers and grey pubescence. The followingtreatments were used:

Treatment 1: No glyphosate spray before or after inoculation

Treatment 2: One application of glyphosate (48 oz./A) (1.0 kg/ha ofactive ingredient) three days before inoculation

Treatment 3: Twice the amount of glyphosate as in Treatment 2 (96 oz./A)(2.0 kg/ha of active ingredient) applied three days before inoculation

Treatment 4: One application of glyphosate (48 oz./A) three days beforeinoculation, and one application (48 oz./A) (1.5 kg/ha of activeingredient) when symptoms of soybean rust first appeared.

Treatment 5: No glyphosate spray before inoculation, and one application(48 oz./A) (1.5 kg/ha of active ingredient) when symptoms of soybeanrust first appeared.

The results of this example are recorded in FIGS. 1-3. With reference toFIGS. 1-3, treatments 2 and 3 demonstrate that glyphosate treatmentexerts a dose-dependent effect on soy rust. Treatments 4 and 5demonstrate that glyphosate treatment of soybean infected with soy rusthas a curative effect.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the disclosed methodswithout departing from the scope or spirit of the disclosure. Otherembodiments of the methods will be apparent to those skilled in the artfrom consideration of the specification and practice of the proceduresdisclosed herein. It is intended that the specification and examples beconsidered as exemplary only, with a true scope and spirit of theinvention being indicated by the following claims.

1. A method for reducing disease on a crop infected with at least onepathogen, comprising: providing an herbicide resistant crop; andtreating the crop with glyphosate, thereby reducing the effects of thepathogen on the crop.
 2. The method according to claim 1, wherein thecrop is selected from glyphosate resistant soybeans and glyphosateresistant wheat.
 3. The method according to claim 1, wherein treatingthe crop comprises at least two separate applications of glyphosate. 4.The method according to claim 3, wherein the more than two separateapplications of glyphosate are applied at least about seven days apart.5. The method according to claim 1, wherein treating the crop comprisestreating the crop with from greater than about 1.0 kg/ha to about 3.0kg/ha of glyphosate.
 6. The method according to claim 1, whereintreating the crop comprises treating the crop with from greater thanabout 1.0 kg/ha to about 2.0 kg/ha of glyphosate.
 7. The methodaccording to claim 1, wherein treating the crop comprises treating thecrop with from about 1.5 kg/ha to about 2.0 kg/ha of glyphosate.
 8. Themethod of claim 5, wherein treating the crop with glyphosate comprisesat least two separate applications of glyphosate.
 9. The method of claim1, wherein the pathogen is a fungal pathogen.
 10. The method of claim 1,wherein the pathogen is a foliar pathogen.
 11. The method of claim 1,wherein the pathogen is a species of Rhizoctonia, Gaeumannomyces,Phakopsora or Puccinia.
 12. The method of claim 1, wherein the pathogenis Phakopsora.
 13. The method of claim 12, wherein the crop isglyphosate resistant soybean.
 14. The method of claim 1, wherein thecrop is glyphosate resistant wheat.
 15. The method of claim 1, whereinthe yield is from about 5% to about 20% higher than a crop not treatedwith glyphosate.
 16. The method of claim 1, wherein the crop isglyphosate resistant wheat and the crop is treated with glyphosate at astage between the 3 leaf stage and the flowering stage.
 17. The methodof claim 1, wherein the crop is glyphosate resistant soybean and thesoybeans and the crop is treated between emergence and the floweringstage.
 18. The method of claim 1, wherein treating the crop withglyphosate comprises treating the crop with glyphosate prior to thedisplay of a symptom of pathogen presence.
 19. The method of claim 1,further comprising harvesting the crop thereby yielding a harvestedcrop.
 20. A harvested crop produced by the method of claim
 19. 21. Amethod for reducing disease on a wheat crop with at least one pathogen,comprising: providing an herbicide resistant wheat crop; and treatingthe wheat crop with an herbicide after emergence of the herbicideresistant wheat crop, thereby reducing the effects of the pathogen onthe wheat crop.
 22. The method according to claim 21, wherein theherbicide resistant wheat crop is glyphosate resistant.
 23. The methodaccording to claim 21, further comprising treating the wheat crop priorto emergence.
 24. The method according to claim 21, wherein theherbicide is glyphosate.
 25. The method according to claim 21, whereinthe herbicide is a 5-enolpyruvylshikimate-3-phosphate synthaseinhibitor.
 26. The method according to claim 21, wherein the pathogen isa soilborne pathogen.
 27. The method according to claim 21, wherein thepathogen is a fungal pathogen.
 28. The method according to claim 21,wherein the pathogen is a species of Rhizoctonia, Gaeumannomyces,Phakopsora or Puccinia.
 29. The method according to claim 28, whereinthe pathogen is Gaeumannomyces graminis var tritici.
 30. The methodaccording to claim 21, wherein the pathogen is a foliar pathogen. 31.The method according to claim 21, wherein the pathogen causes striperust, stem rust or leaf rust.
 32. The method according to claim 31,wherein the pathogen is Puccinia striiformis.
 33. The method accordingto claim 21, wherein pathogen activity is decreased for at least 21 daysafter herbicide application.
 34. The method of claim 22, wherein theglyphosate resistant wheat crop is treated with from about 0.5 kg/ha toabout 2.0 kg/ha glyphosate, thereby increasing the yield of the wheat,wherein the yield is at least about 5% higher than a glyphosatesensitive wheat crop.
 35. The method according to claim 21, whereinglyphosate is applied at a density of from about 0.5 kg/ha to about 1.5kg/ha.
 36. The method according to claim 21, wherein glyphosate isapplied at a density of from about 0.5 kg/ha to about 1.0 kg/ha.
 37. Themethod according to claim 34, wherein the yield is from about 5% toabout 20% higher.
 38. The method according to claim 1, wherein the atleast one pathogen is a rust.
 39. The method according to claim 38,wherein the rust is selected from the group consisting of stem rust,stripe rust, leaf rust and soybean rust.
 40. The method according toclaim 1, wherein treating the crop comprises treating the crop withglyphosate at a density of greater than about 1.0 kg/ha of glyphosate41. A method for reducing disease on a crop infected with at least onepathogen, comprising: providing an herbicide resistant crop, wherein thecrop is selected from glyphosate resistant wheat and glyphosateresistant soybeans; treating the crop with glyphosate at a density ofgreater than about 1.0 kg/ha of glyphosate, thereby reducing the effectsof the pathogen on the crop.
 42. A method for inhibiting or treating soyrust in a glyphosate resistant soybean crop, comprising the step oftreating a glyphosate resistant soybean crop which either has or issusceptible of having soy rust with glyphosate under conditionssufficient to inhibit or treat soy rust.
 43. The method of claim 42wherein said glyphosate is present in a herbicide composition.
 44. Amethod for inhibiting or treating stripe rust in a glyphosate resistantwheat crop, comprising the step of treating a glyophosate resistantwheat crop which either has or is susceptible of having stripe rust withglyphosate under conditions sufficient to inhibit or treat stripe rust.45. The method of claim 44 wherein said glyphosate is present in aherbicide composition.
 46. A method for preventing or treating fungaldisease, or reducing adverse effects of fungal disease in a glyphosateresistant wheat or soybean crop, comprising the step of treating aglyphosate resistant wheat or soybean crop which either has or issusceptible of having a fungal disease with glyphosate under conditionssufficient to inhibit growth or proliferation of fungal pathogens insaid glyphosate resistant wheat or soybean crop.
 47. The method of claim46 wherein said glyphosate is present in a herbicide composition. 48.The method of claim 46 wherein said fungal pathogens are selected fromthe species selected from Rhioctonia, Gaeumannomyces, Phakopsora, andPuccinia.
 49. The method of claim 46 wherein said fungal pathogens areimplicated in soy rust or stripe rust.
 50. A method of using glyphosateto inhibit or treat soy rust in a glyphosate resistant soybean crop,comprising the step of treating a glyphosate resistant soybean cropwhich either has or is susceptible of having soy rust with glyphosateunder conditions sufficient to inhibit or treat soy rust.
 51. The methodof claim 50 wherein said glyphosate is present in a herbicidecomposition.
 52. A method of using glyphosate to inhibit or treat striperust in a glyphosate resistant wheat crop, comprising the step oftreating a glyophosate resistant wheat crop which either has or issusceptible of having stripe rust with glyphosate under conditionssufficient to inhibit or treat stripe rust.
 53. The method of claim 52wherein said glyphosate is present in a herbicide composition.
 54. Amethod of using glyphosate to prevent or treat fungal disease, or toreduce adverse effects of fungal disease in a glyphosate resistant wheator soybean crop, comprising the step of treating a glyphosate resistantwheat or soybean crop which either has or is susceptible of having afungal disease with glyphosate under conditions sufficient to inhibitgrowth or proliferation of fungal pathogens in said glyphosate resistantwheat or soybean crop.
 55. The method of claim 54 wherein saidglyphosate is present in a herbicide composition.
 56. The method ofclaim 54 wherein said fungal pathogens are selected from the speciesselected from Rhioctonia, Gaeumannomyces, Phakopsora, and Puccinia. 57.The method of claim 54 wherein said fungal pathogens are implicated insoy rust or stripe rust.